There are times when the electric field generated by a sensing element used in a capacitive sensing system requires directionality or pattern shaping to enhance the overall utility of the sensing system.
It is appreciated that a portion of an electric field radiated from a sensing element will be readily absorbed into a grounded conductive object standing within proximity of its radiated field. An example of such an interaction between a radiated electric field and a grounded object can be illustrated by consideration of a capacitive sensing system used on a conventional automatic garage door.
Generally, a sensing element would be mounted along the bottom edge of a garage door such that the sensing element extends along the entire width of the door before terminating just short of the door guide rails. In this manner, the extreme ends of the sensing element are adjacent the opposing guide rails on which the door moves during opening and closing. As such, portions of the sensing element's radiated field, particularly the portions near the grounded guide rails, will be absorbed therein causing the sensing field to be smaller at the ends of the sensing element. Hence, the grounded object effectively operates on the radiated field to effect its radiated shape or pattern.
The present invention provides a method of controlling the shape or pattern of a radiated electric field to enhance the overall utility of a capacitive sensing system.